In covered hopper railway cars many materials are shipped dry. At destination water is added to the lading and the mixture is agitated with air distributed to the mixture through openings located in a loop in the hopper outlet.
However, lading often enters the openings in the loop. The openings become clogged with lading so that air cannot exit from the loop. Furthermore, the loop often gradually becomes filled with lading which reduces the amount of air which can be passed through the loop for agitation. This results in a longer time required to form a solution or slurry of the lading. In some instances the air loop becomes so filled with lading that the loop becomes completely blocked, and no air can circulate. This necessitates removing the outlet from the car and removing the air loop from the outlet for cleaning. Such cleaning is expensive and disruptive because the outlet must be temporarily taken out of service.